Method and apparatus for providing an alert with information signal between a mobile switching center and a base station

ABSTRACT

The invention is a method and apparatus for providing an Alert With Information Message signal between a mobile switching center and a base station in a cellular communication system. The invention recognizes that current provisions of the IS-634 standard lack support for certain required functionality on the interface between a mobile switching center and a base station, or the A-Interface. An Alert With Information Message signal is introduced on the A-Interface to support the required functionality. Introduction of the Alert With Information Message provides support for reliable call processing on the A-Interface for the call waiting procedure, the hard handoff procedure, and the resolution of a glare condition.

BACKGROUND OF THE INVENTION

[0001] I. Field of the Invention

[0002] The present invention relates to spread spectrumtelecommunications systems. More particularly, the present inventionrelates to a novel and improved messaging method and apparatus in a CDMAcommunication system.

[0003] II. Description of the Related Art

[0004] The use of code division multiple access (CDMA) modulationtechniques is one of several techniques for facilitating communicationsin which a large number of system users are present. Although othertechniques such as time division multiple access (TDMA), frequencydivision multiple access (FDMA), and amplitude modulation (AM) schemessuch as amplitude companded single sideband (ACSSB) are known, CDMA hassignificant advantages over these other techniques. The use of CDMAtechniques in a multiple access communication system is disclosed inU.S. Pat. No. 4,901,307, entitled “SPREAD SPECTRUM MULTIPLE ACCESSCOMMUNICATION SYSTEM USING SATELLITE OR TERRESTRIAL REPEATERS,” assignedto the assignee of the present invention and incorporated by referenceherein.

[0005] In the CDMA cellular system, a large number of mobile telephonesystem users, each having a transceiver, communicates through satelliterepeaters or terrestrial stations which are also referred to as cells.Each cell includes a physical plant called a base station. A cell coversa limited geographic area and routes calls carried over cellulartelephones to and from a telecommunication network via a mobileswitching center. When a cellular telephone user moves into thegeographic area of a new cell, the routing of that user's call may beeventually made through the new cell by a process called a “handoff”.

[0006] A cellular telephone or, more specifically, a mobile station,broadcasts a signal that is received by a base station. The signal isthen relayed to a mobile switching center which in turn routes thesignal to the public switched telephone network and to telephone linesor other mobile stations. Similarly, a signal may be transmitted fromthe public switched telephone network to a mobile station via a basestation and a mobile switching center. The communications channelallocated for communication of information between the mobile stationand the base station is called the traffic channel.

[0007] The interface between the mobile station and the base station isreferred to as the Air-Interface. The telecommunications industryassociation (TIA) has provided a standard for CDMA call processing onthe Air-Interface entitled “IS-95-A Mobile Station - Base StationCompatibility Standard for Dual Mode Wideband Spread Spectrum CellularSystem,” hereinafter IS-95-A, which is incorporated by reference. Theinterface between the base station and the mobile switching center isreferred to as the A-Interface. The TIA has provided for call processingon the A-Interface through the standard provided in “IS-634 MobileSwitching Center-Base Station Interface for Public 800 MHz,” which isalso incorporated by reference. IS-95-A and IS-634 both define themessages and signals that are sent on their respective interfaces forthe operation of a CDMA cellular telephone call.

[0008] The call flow in a CDMA environment requires processing on boththe Air-Interface and the A-Interface. The successful progression of acall requires that the proper messages and signals are sent at the righttimes on both the Air-Interface and the A-Interface. The IS-634 standardis being developed to provide for call processing on the A-Interface. Anumber of problems and deficiencies are present in IS-634 whichcurrently does not support some of the necessary operations on theA-Interface. Some of these problems and deficiencies are recognized andsolved by the present invention in the manner described below.

SUMMARY OF THE INVENTION

[0009] The present invention is a novel and improved method andapparatus for providing a new message on the interface between a mobileswitching center and a base station, also known as the A-Interface, of acellular telephone system. The present invention recognizes that theA-Interface, as presently defined by the IS-634 standard, does notsupport some of the operations necessary for reliable call processing.Introduction of the new message will provide support for requiredfunctionality on the A-Interface.

[0010] The present invention recognizes that improvements are needed forthe A-Interface to reliably handle the call waiting and the hard handoffprocedures. In addition, a better technique is needed for resolving aglare condition. An Alert With Information Message is introduced on theA-Interface to improve the operation of these procedures.

[0011] Using the call waiting feature, a mobile station may have a firstparty of a public switched telephone network put on hold while beingconnected to a second party. If the second party hangs up, thenaccording to the current procedure, a Release/Clear Message (or anequivalent message) is sent to the mobile station, causing the mobilestation to release its traffic channel. A new traffic channel must thenbe reestablished to reconnect the mobile with the first party. Thepresent invention recognizes that the current procedure is unreliable inthat difficulties may arise in the process of reconnecting the mobilewith the first party. Moreover, Air-Interface resources are usedinefficiently as the current procedure requires the release of thetraffic channel and the reassignment of a new channel. To overcome theseshortcomings, an Alert With Information Message is sent on theA-Interface to the base station, triggering the transmittal of an AlertWith Information Message on the Air-Interface. Upon receipt of the AlertWith Information Message, the mobile station is prompted to transmit aConnect Message to the mobile switching center via a base station. Themobile switching center then reconnects the first party to the mobilestation, without the need to reestablish a new traffic channel.

[0012] A hard handoff occurs in a cellular system when a mobile stationmoves from the coverage area of one base station to the coverage area ofanother base station. During a mobile station terminated call, in orderfor the mobile to undertake handoff, it must first receive an Alert WithInformation Message transmitted by the base station. Under currentprocedure, the Alert With Information Message is generated andtransmitted solely by the base station in whose coverage area the mobileis currently located. The present invention recognizes that the currentprocedure may cause the hard handoff procedure to be unreliable. If themobile moves from the coverage area of a first base station to thecoverage area of a second base station, the mobile station may neverreceive the Alert With Information Message from the first base station,resulting in a dropped call. Thus, the present invention provides for anAlert With Information Message to be generated and transmitted by themobile switching center. While the mobile station is moving from thecoverage area of the first base station to that of the second basestation, the mobile switching center transmits the Alert WithInformation Message to the second base station. The second base stationin turn transmits an Alert With Information Message to the mobilestation. Having received the Alert With Information Message, handoff cannow proceed without the call being dropped.

[0013] A mobile subscriber may attempt to originate a call while anotherparty is attempting to call the same mobile subscriber, resulting in aglare condition. The Air-Interface standard, IS-95-A, provides themobile the option of aborting the call that it is originating andresponding to the call that it is receiving. However, the presentinvention recognizes that the mobile may not successfully receive thecall because the base station is not configured to transmit the propermessages to the mobile when a glare condition occurs. In order for themobile subscriber to respond to a call, it is necessary for the mobileto receive an Alert With Information Message. However, the standardcurrently does not address this situation. As a result, the call may bedropped. The present invention recognizes that the resolution of theglare condition should be undertaken at the mobile switching center. Themobile switching center, upon receiving a message indicative of a mobileoriginating a call and subsequently receiving a message indicative ofthe same mobile receiving a call, should recognize that the mobile isproceeding with receiving a call. The mobile switching center shouldthen transmit an Alert With Information Message to the base station,triggering the base station to transmit an Alert With InformationMessage to the mobile station. As the Alert With Information Message isreceived by the mobile station, the glare condition is resolved withoutthe call being dropped.

[0014] Benefits and advantages of the present invention will becomeapparent from the following description of the preferred embodiment whenit is considered with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The features, objects, and advantages of the present inventionwill become more apparent from the detailed description set forth belowwhen taken in conjunction with the drawings in which like referencecharacters identify correspondingly throughout and wherein:

[0016]FIG. 1 is a block diagram presenting a schematic overview of anexemplary CDMA cellular telephone system in accordance with the presentinvention;

[0017]FIG. 2 is a block diagram illustrating an exemplary call-waitingscenario according to the current IS-634 standard;

[0018]FIG. 3 is a block diagram illustrating a call-waiting scenarioaccording to the present invention;

[0019]FIG. 4 is a flow chart illustrating an exemplary embodiment of theprocessing steps involved in call-waiting as implemented by theprocessing elements of FIG. 3;

[0020]FIG. 5 is a block diagram illustrating an exemplary hard handoffscenario in a cellular telephone system;

[0021]FIG. 6 is a state diagram illustrating the states of a mobilestation in a mobile station terminated call;

[0022]FIG. 7 is a block diagram illustrating an exemplary embodiment ofthe hard handoff scenario according to the present invention;

[0023]FIG. 8 is a flow chart illustrating an exemplary embodiment of theprocessing steps involved in hard handoff as implemented by theprocessing elements of FIG. 3;

[0024]FIG. 9 is a block diagram illustrating an exemplary embodiment ofthe processing elements involved in the resolution of a glare condition;and

[0025]FIG. 10 is a flow diagram illustrating the occurrence and theresolution of a glare condition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] An exemplary CDMA cellular mobile telephone system in which thepresent invention is embodied is illustrated in FIG. 1. The CDMAcellular telephone system is indicated generally by 9 and includes amobile switching center (MSC) 10, also referred to as a mobile telephoneswitching office (MTSO), that includes interface and processingcircuitry for providing system control to the base stations. The MSC 10routes telephone calls from a public switched telephone network (PSTN)11 to the appropriate base station for transmission to the appropriatemobile station. The MSC 10 also controls the routing of calls from themobile stations via one or more base stations to the PSTN 11. Inaddition, the MSC 10 may direct calls between mobile stations via theappropriate base stations. The MSC 10 may be coupled to the basestations by various conventional means, such as dedicated telephonelines, optical fiber links, or by radio frequency communications.

[0027] It should be understood that although the present invention isdescribed herein within the context of a CDMA cellular communicationssystem, it is equally applicable to other types of communicationsystems, such as the personal communication system (PCS). Furthermore,systems utilizing other well known transmission modulation schemes suchas TDMA and FDMA as well as other spread spectrum systems may employ thepresent invention.

[0028] In FIG. 1, two exemplary base stations (BSs), 12 and 14, alongwith two exemplary mobile stations (MSs) 16 and 18, each including acellular telephone, are illustrated. Arrows 20 a and 20 b representforward and reverse code channels that define a possible communicationlink between BS 12 and MS 16. Arrows 22 a and 22 b define a possiblecommunication link between BS 12 and MS 18. Similarly, BS 14 canestablish a two-way communication link with MS 18 as represented byarrows 24 a and 24 b and with MS 16 as represented by the arrows 26 aand 26 b.

[0029] As previously mentioned, the interface between BSs 12 and 14 andMSs 16 and 18 is called the Air-Interface, and in the exemplaryembodiment, call processing on the Air-Interface is governed by IS-95-A.Also as previously mentioned, the interface between MSC 10 and BSs 12and 14 is called the A-Interface, and call processing on the A-Interfaceis governed by IS-634. The present invention recognizes that theA-Interface as currently defined by IS-634 lacks support for some of thenecessary functionality for reliable call processing. In addition, thepresent invention recognizes that introduction of a new message on theA-Interface will cure some of the deficiencies of the A-Interface.

[0030] An exemplary procedure in which deficiencies are recognized onthe A-Interface is the call waiting procedure. Call waiting is onefeature available to the CDMA cellular subscriber. The call waitingfeature allows a cellular subscriber to toggle between two parties onthe telephone network. Call waiting may be provided in a CDMA telephonesystem according to the techniques disclosed in copending U.S. patentapplication Ser. No. 08/535,998, entitled “Early Detection of Mobile toMobile,” filed Sep. 29, 1995, which is assigned to the assignee of thepresent invention and incorporated by reference herein.

[0031] An exemplary call waiting scenario is illustrated in FIG. 2. InFIG. 2, party 1 28 and party 2 30 are two parties of a PSTN. A call hasbeen established between MS 32 and party 1 28. A traffic channel hasbeen set up between MS 32 and BS 34 on the Air-Interface. Furthermore,BS 34 is connected to MSC 36 on the A-Interface by any of variousconventional means as described above.

[0032] If party 2 30 calls MS 32 while MS 32 is communicating with party1 28, MSC 36 will send signaling data to BS 34 indicating that anotherparty is attempting to contact MS 32. The means for combining trafficdata and signaling data is described in detail in U.S. Pat. No.5,511,073, entitled “METHOD AND APPARATUS FOR THE FORMATTING OF DATA FORTRANSMISSION,” assigned to the assignee of the present invention andincorporated by reference herein. To inform MS 32 that another call iscoming in, an alerting signal is relayed by BS 34 to MS 32 either by aFlash With Information message or an inband tone. Then, MS 32 can invokethe call waiting feature by pushing a specific key on the MS keypad.This causes the generation of a Flash With Information Message, which issent on the Air-Interface to BS 34, which in turn relays the Flash WithInformation Message on the A-Interface to MSC 36. MSC 36 then connectsparty 2 30 to MS 32 while putting party 1 on hold. Thereafter, MS 32 maytoggle between party 1 28 and party 2 30 by pushing the key on thekeypad to cause the generation of the Flash With Information Message.Each time MSC 36 receives the Flash With Information Message, itconnects MS 32 to the party that was previously put on hold and puts onhold the party that was previously on the line.

[0033] Referring still to FIG. 2, assume that party 1 28 is on hold andMS 32 is connected to party 2 30. If party 2 30 hangs up, then accordingto the current procedure, the network which is servicing party 2generates a Release Message. This Release Message propagates to MSC 36,which then sends the Release Message to BS 34 on the A-Interface. BS 34in turn sends a Release Message to MS 32 on the Air-Interface to causeMS 32 to release its traffic channel. MSC 36 then signals to BS 34 thatparty 1 28 is attempting to contact MS 32. This causes BS 34 to send aPaging message to MS 32 to indicate that a call is incoming. Inresponse, MS 32 generates a Paging Response Message which is transmittedto BS 34. BS 34 then transmits the Paging Response Message to MSC 36. Onreceipt of a Paging Response Message, MSC 36 assigns a new trafficchannel to MS 32 and MS 32 is reconnected to party 1 28.

[0034] The present invention recognizes that this procedure has severalshortcomings. First, it does not efficiently use the Air-Interfaceresource, since it requires the release of the traffic channel,re-paging of MS 32 and the assignment of a new traffic channel. Further,the need to obtain a new traffic channel makes it difficult toreestablish the connection between MS 32 and party 1 28. If MS 32 movesaway from BS 34 from which it is released, the page from MSC 36 may notbe received by MS 32. At the very least, this increases the amount oftime that party 1 28 has to wait for the reconnection with MS 32. Thereis also the possibility that the connection between MS 32 and party 1 28cannot be reestablished, resulting in a dropped call. A better procedureis needed to handle the procedure for releasing party 2 30 from MS 32wherein MS 32 is using the call waiting feature.

[0035] To overcome the shortcomings, the present invention introduces anew message for the A-Interface. A preferred embodiment of the presentinvention is illustrated in FIG. 3. The preferred embodiment providesfor a new message, an Alert With Information Message, on theA-Interface. The Alert With Information Message is currently availableon the Air-Interface under IS-95-A. According to IS-95-A, the Alert WithInformation Message is sent by a base station to a mobile station tocause the mobile to ring and to transition from a Conversation State toa Waiting For Answer State, expecting the mobile user to intervene. Byproviding for an Alert With Information Message on the A-Interface, themobile switching center can better control the progress of the callwaiting procedure.

[0036] Referring to FIG. 3, assume again that party 1 28 is on hold andMS 32 is in communication with party 2 30. If party 2 30 then hangs up,the network servicing party 2 30 generates a Release Message asdescribed above. In the preferred embodiment, when the Release Messagecomes from the network, MSC 36 intercepts it, and message generator 38in MSC 36 generates an Alert With Information Message signal, which issent to BS 34 on the A-Interface. Message receiver 40 in BS 34 receivesthe Alert With Information Message, and BS 34 in turn sends an AlertWith Information Message to MS 32 on the Air-Interface. When MS 32receives the Alert With Information Message, it generates an alertingsignal in the mobile and waits for the subscriber to answer. When thesubscriber answers by pressing a key on keypad of MS 32, a ConnectMessage generated by MS 32 is sent to BS 34 and forwarded to MSC 36. Onreceiving the Connect Message, MSC 36 connects party 1 28 to MS 32.

[0037] In the preferred embodiment, by not permitting the ReleaseMessage (or a Clear Message) from the network to be sent to MS 32, MS 32is not caused to release the traffic channel when party 2 30 hangs up.As a result, there is no need to expend additional Air-Interfaceresources for the assignment of a new traffic channel. Furthermore, thepreferred embodiment does not require MS 32 to be paged following therelease of the traffic channel to indicate that party 1 28 is stillwaiting to be reconnected with MS 32. Consequently, the risk that MS 32will move away from the coverage area of BS 34 and not receive the pageis eliminated.

[0038] A brief illustration of the steps involved in call waiting asdescribed in the embodiment above is shown in FIG. 4. FIG. 4 shows aflow chart illustrating some of the steps involved in the processing asdiscussed with reference to FIG. 3.

[0039] Another procedure in which deficiencies are recognized on theA-Interface is the handoff procedure. In a cellular communicationsystem, a handoff must take place when a mobile station moves from thecoverage area of one base station to another base station. A geographicarea in a cellular system is divided up into cells. Each cell isserviced by a corresponding base station. In a hard handoff environment,as a mobile station moves from one cell to another cell, communicationwith the original base station is terminated before communication withthe subsequent base station is established. In a soft handoffenvironment, communication with the subsequent base station isestablished before terminating communication with the original basestation. U.S. Pat. No. 5,267,261, which is incorporated by reference andassigned to the assignee of the present invention, discloses a methodand system for providing soft handoff.

[0040] The hard handoff procedure in a mobile terminated call may beunderstood with reference to FIGS. 5 and 6. As illustrated in FIG. 5, asMS 42 moves from the coverage area of BS1 44 to BS2 46, a connectionneeds to be established between MS 42 and BS2 46 while MS 42 needs to bedisconnected from BS1 44. Both BS1 44 and BS2 46 are shown to beconnected to MSC 48 in FIG. 5. However, it should be understood that ahard handoff can also occur when a mobile station moves from the controlof one mobile switching center to another. In fact, the different mobilestation controllers may support different modulation techniques such asTDMA or FDMA.

[0041] In FIG. 6, the states of a mobile station in a mobile terminatedcall are briefly illustrated. The states are summarized herein andexplained more fully in the aforementioned document IS-95-A, pages 6-160to 6-161.

[0042] The progression of the hard handoff procedure is dependent on thestate of the mobile station. Referring to FIG. 6, in a mobile stationterminated call, the mobile is in the Traffic Channel InitializationState, shown by block 50, when a traffic channel has been establishedbetween a mobile station and a base station. Upon receipt of a BaseStation Acknowledgment Order from the base station, the mobile movesinto the Waiting For Order State, shown by block 52. The mobile stationthen transitions into the Waiting For Answer State, illustrated by block54, when it receives an Alert With Information Message from the basestation. When the mobile station subscriber answers the call by pushinga specific key on the mobile station keypad, the mobile transitions intothe Conversation State, represented by block 56. The mobile transitionsinto the Release State, shown by block 58, when conversation terminates.

[0043] According to the current procedure, a mobile station should be inthe Waiting For Answer State 54 or the Conversation State 56 during hardhandoff. If the mobile is in any other state, the call is likely to bedropped during hard handoff. Thus, the mobile station must receive anAlert With Information Message transmitted by the base station on theAir-Interface before the mobile station undertakes handoff. Otherwise,the handoff procedure would be unreliable. Referring again to FIG. 5,assume that MS 42 is in the coverage area of BS1 44. If MS 42subsequently moves from the coverage area of BS1 44 to the coverage areaof BS2 46 while MS 42 is in the Waiting For Order State 52, MS 42 maynot receive the Alert With Information Message sent by BS1 44. Withoutreceiving the Alert With Information Message, MS 42 cannot transitioninto the Waiting For Answer State 54 in the coverage area of BS2 46. Asa result, the call will be dropped while handoff is in progress. Thus,the present invention recognizes that a better method for handling hardhandoff in a mobile station terminated call is necessary.

[0044] As previously described, providing an Alert With InformationMessage on the A-Interface overcomes the shortcomings in the callwaiting procedure. The present invention recognizes that providing anAlert With Information Message on the A-Interface will also overcome theshortcomings in a hard handoff procedure in a mobile station terminatedcall. Further, it should be understood that the present inventionapplies to hard handoff procedures in a variety of communicationenvironments, including CDMA, TDMA, or FDMA.

[0045] A preferred embodiment of the use of an Alert With InformationMessage on the A-Interface in a hard handoff procedure is illustrated inFIG. 7 with reference to FIG. 6. An Alert With Information Message isgenerated by message generator 50 in MSC 48 and sent to message receiver52 in BS2 46. The Alert With Information Message is sent on theA-Interface when MS 42 is moving from the coverage area of BS1 44 to thecoverage area of BS2 46 while in the Waiting For Order State. After BS246 receives the Alert With Information Message from MSC 48, BS2 46 thensends an Alert With Information Message to MS 42 on the Air-Interface.Having received the Alert With Information Message, MS 42 can transitioninto the Waiting For Answer State 54 while in the coverage area of BS246, and handoff can occur without the call being dropped. Thus, byproviding for an Alert With Information Message on the A-Interface, MSC48 has better control of the hard handoff procedure. Since MSC 48 cansend the Alert With Information Message to BS2 46, causing BS2 46 tosend the Alert With Information Message to MS 42, MS 42 does not need torely on receiving the Alert With Information Message from BS1 44 inorder to transition into the Waiting For Answer State 54. Consequently,handoff can occur without the call being dropped. A flow chartillustrating some of the processing steps involved in hard handoff asdescribed in the embodiment above is shown in FIG. 8.

[0046] Still another procedure in which deficiencies are recognized onthe A-Interface is the handling of a glare condition. A glare conditionmay occur when a mobile subscriber attempts to initiate a call whileanother party is attempting to call the mobile subscriber. A callinitiated by a mobile subscriber is referred to as a mobile stationoriginated call, while a call made to a mobile subscriber is referred toas a mobile station terminated call.

[0047] The glare condition may be better understood by referring back toFIG. 1. In a mobile station originated call, an Origination Message istransmitted from a mobile station, such as MS 16, to a base station,such as BS 12, upon initiation of a call by MS 16. After transmission ofthe Origination Message but before a connection is established betweenMS 16 and the called party (party A of PSTN 11), another party (party Bof PSTN 11) may attempt to contact the mobile subscriber and MSC 10 maypage MS 16, resulting in a glare condition. The Air-Interface standard,IS-95-A, permits MS 16 the option of aborting the call to party A andresponding to the call from party B. MS 16 then follows the statetransition sequence for a mobile station terminated call as illustratedin FIG. 6.

[0048] Referring now to FIG. 6, in a mobile station terminationscenario, the mobile expects to receive an Alert With InformationMessage to transition from the Waiting For Order State, represented byblock 52, to the Waiting For Answer State, represented by block 54. Ifthe Alert With Information Message is not received, the mobile wouldtime out and release the call.

[0049] It is recognized by the present invention that current proceduresunder IS-95-A and IS-634 do not properly resolve the glare condition.Currently, the base station is not configured to transmit an Alert WithInformation Message to the mobile station upon occurrence of a glarecondition. The problem is explained in greater detail with reference toFIG. 9. Referring to FIG. 9, when MS 60 originates a call, anOrigination Message is sent from MS 60 to BS 62. In response to theOrigination Message, BS 62 transmits a BS Acknowledgment Order to MS 60.Meanwhile, MSC 64 receives an incoming call to the same MS 60, unawareof the origination effort in progress, and sends a Paging RequestMessage to BS 62 to initiate a mobile terminated call setup. BS 62 inturn sends a Page Message containing the MS address, and the PageMessage is received by MS 60.

[0050] Due to the mobile origination attempt, BS 62 constructs a ServiceRequest Message and sends the message to MSC 64. However, afterreceiving the Page Message, MS 60 aborts the origination call setup, andresponds by transmitting a Paging Response Message, which is received byBS 62. But because MSC 64 had received a Service Request Message from BS62, MSC 64 in response sends an Assignment Request Message to BS 62,requesting assignment of Air-Interface resources for the mobile stationoriginated call. Upon receipt of the Assignment Request Message, BS 62assumes that a mobile station originated call is in progress, and doesnot transmit an Alert With Information Message to MS 60. As a result, MS60 times out waiting for the Alert With Information Message, and themobile station terminated call is dropped.

[0051] In order to better resolve the glare condition, the presentinvention provides for still another use of the Alert With InformationMessage on the A-Interface. First, note that after BS 62 receives aPaging Response Message from MS 60, BS 62 in turn sends a PagingResponse Message to MSC 64. Then, in a preferred embodiment, the presentinvention provides for an Alert With Information Message to betransmitted on the A-Interface if MSC 64 receives a Service RequestMessage and then a Paging Response Message. Still referring to FIG. 9,it can be seen that the Alert With Information Message may be generatedin MSC 64 by message generator 66, while the Alert With InformationMessage may be received in BS 62 by message receiver 68. After BS 62receives the Alert With Information Message from MSC 64, BS 62 thensends an Alert With Information Message to MS 60 on the Air-Interface.Having received the Alert With Information Message, MS 60 can transitioninto the Waiting For Answer State, and the glare condition is resolvedwithout the call being dropped.

[0052] Referring now to FIG. 10, a flow chart illustrating some of theprocessing steps involved in the resolution of the glare condition asdiscussed with reference to FIG. 9 is shown. An Alert With InformationMessage is provided on the A-Interface to resolve the glare condition.

[0053] The present invention recognizes that for the call waiting, hardhandoff, and resolution of a glare condition procedures, there arecertain deficiencies in call processing on the A-Interface as currentlydefined by IS634. By providing an Alert With Information Message on theA-Interface, the present invention overcomes these deficiencies. TheAlert With Information Message is already available on the Air-Interfaceunder IS-95-A to cause a mobile station to transition from the WaitingFor Order State to the Waiting For Answer State. An Alert WithInformation Message is provided on the A-Interface to trigger thetransmittal of the Alert With Information Message on the Air-Interface,solving the problems of the call-waiting and handoff procedures as wellas resolving the glare condition.

[0054] The previous description of the preferred embodiments is providedto enable any person skilled in the art to make or use the presentinvention. The various modifications to these embodiments will bereadily apparent to those skilled in the art, and the generic principlesdefined herein may be applied to other embodiments without the use ofthe inventive faculty. Thus, the present invention is not intended to belimited to the embodiments shown herein but is to be accorded the widestscope consistent with the principles and novel features disclosedherein.

I claims
 1. A telecommunications messaging system, comprising: a messagegenerator in a mobile switching center for generating a message signal,said message signal for transmission to a base station for triggeringsaid base station to transmit a subsequent message signal to a mobilestation; and a message receiver in said base station for receiving saidmessage signal; wherein said message signal is generated upon detectionof a glare condition by said mobile switching center.
 2. The messagingsystem of claim 1 wherein said glare condition is detected when saidmobile switching center receives a message indicative of a mobilestation call origination and a message indicative of a mobile stationcall termination in quick succession.
 3. The messaging system of claim 2wherein said message indicative of a mobile station call origination isa Service Request Message and said message indicative of a mobilestation call termination is a Paging Response Message.
 4. The messagingsystem of claim 1 wherein said message signal is an Alert WithInformation Message signal and said subsequent message signal is anAlert With Information Message signal.
 5. The messaging system of claim3 wherein said message signal is an Alert With Information Messagesignal and said subsequent message signal is an Alert With InformationMessage signal.
 6. A cellular communication system, comprising: a mobilestation; a base station in communication with said mobile station via anAir-Interface, said base station defining a first cellular coveragearea; a mobile switching center in communication with said base stationvia an A-Interface; a message generator at said mobile switching centerfor generating a message signal for transmission to said first basestation on said A-Interface; and a message receiver at said base stationfor receiving said message signal, wherein upon receipt of said messagesignal, said first base station transmits a subsequent message signal tosaid mobile station on said Air-Interface; wherein said messagegenerator generates said message signal when said mobile switchingcenter detects a glare condition.
 7. The cellular communication systemof claim 6 wherein said message signal is an Alert With InformationMessage signal and said subsequent message signal is an Alert WithInformation Message signal.
 8. The cellular communication system ofclaim 6 wherein said glare condition is detected when said mobileswitching center receives a message indicative of a mobile station callorigination and a message indicative of a mobile station calltermination in quick succession.
 9. The cellular communication system ofclaim 8 wherein said message indicative of a mobile station callorigination is a Service Request Message and said message indicative ofa mobile station call termination is a Paging Response Message.
 10. Thecellular communication system of claim 9 wherein said message signal isan Alert With Information Message signal and said subsequent messagesignal is an Alert With Information Message signal.
 11. A method formessaging between a mobile switching center and a base station,comprising the steps of: detecting the occurrence of a glare condition;generating a message signal in said mobile switching center based on apositive result of said step of detecting; and transmitting said messagesignal to said base station on an A-Interface, wherein upon receipt ofsaid message signal, said base station transmits a subsequent messagesignal to a mobile station on an Air-Interface;
 12. The method of claim11 wherein said step of detecting comprises the steps of: determining ifa message indicative of a mobile station call origination is received atsaid mobile switching center; and determining if a message indicative ofa mobile station call termination is received at said mobile switchingcenter.
 13. The method of claim 12 wherein said message indicative of amobile station call origination is a Service Request Message and saidmessage indicative of a mobile station call termination is a PagingResponse Message.
 14. The method of claim 13 wherein said message signalis an Alert With Information Message signal and said subsequent messagesignal is an Alert With Information Message signal.